The purpose of the Analytical Core is to provide state-of-the-art biochemical analysis of sympathetic function, including measurements of catecholamines, their metabolities, and norepinephrine clearance and spillover. This resource has been critical to the recognition and characterization by our group of new disorders involving the autonomic nervous system, such as dopamine-beta-hydroxylase deficiency, baroreflex failure, neuropathic orthostatic intolerance, and norepinephrine transporter deficiency. A variety of techniques have been established in this Core to support individual projects, including the determination of plasma volume and dynamic fluid shifts. All five projects will utilize this resource. Biochemical evaluation of sympathetic activity will complement other methods of autonomic evaluation detailed in the Clinical Core.